A novel optical film to provide a highly collimated planar light source

In this paper, we proposed a novel optical film 'Collimation Film with Equivalent Focal Reflective Aperture' (CFEFRA) that can collocate with the proper light guide plate (LGP) to provide a highly collimated planar light source (HCPLS) that not only has high intensity peak but also good uniformity. The CFEFRA has micro-cylindrical lenses and inverted-prism-like micro-teeth on its upper surface and lower surface, respectively. The lower micro-teeth that are aligned with the upper lenses can deflect the light emitting from the LGP at large declination into the normal, and then the deflected light with transverse fan-out is further converged by the upper lens to become the collimated light. The exact alignment between the upper and lower micro-structures is fulfilled by the method 'auto-secure-alignment by focusing of a collimated exposure beam'. The vertical and horizontal full width at half maximum (FWHM) of angular intensity of the HCPLS for the optimal case are of 14 and 6 degrees, respectively. Moreover, it still has high optical efficiency with light output of over 90% despite the resultant emitting light is such collimated. Most importantly, CFEFRA just needs to collocate with a relatively low-cost and easily-manufactured LGP so the HCPLS adopting the CFEFRA can be extended for large-sized application. Both optical model and experimental samples are demonstrated in this paper, and the simulation results are consistent with the experimental results. The consistency proves our design concept and optical model are convincible and feasible.